Education

PhD, Biochemistry, Cancer Research UK (formerly Imperial Cancer Research Fund) and University College London (U.K.)

Postdoctoral Fellow, Stanford University (U.S.A.)

Research

One of the central challenges in biology is to elucidate how microenvironments modulate molecular mechanisms and thus global cellular function. The Lillemeier lab studies signal transduction in the plasma membrane of T lymphocytes (T cells) upon their activation by Antigen Presenting Cells (APCs). Major rearrangements of signaling molecules take place during this event, which is most dramatically seen in the formation of signaling microclusters and the immunological synapse (see movie). The lab uses cutting edge super-resolution and dynamic fluorescence microscopy techniques (e.g. PALM and FCCS) in combination with traditional biochemical and molecular biological approaches to study the molecular patterns that regulate and are required for T cell activation and function.

We have found a new type of plasma membrane domains, termed protein islands, and the specific segregation of all membrane-associated proteins within them. These findings inspire a new and unsuspected role for the plasma membrane in the spatio-temporal regulation of T cell activation and membrane biology in general. Specifically, we found that signaling cascades are prearranged into 'building blocks', through the localization of signaling molecule subsets within specific protein islands. Redistribution of these protein islands in response to stimuli can lead to either concatenation and assembly of signal transduction pathways or their dissociation and disassembly. These rearrangements are not diffusion limited but active and directed through cytoskeletal forces and pathway-specific protein-protein interactions.

We welcome students and postdocs to join our lab. For more information please contact Björn Lillemeier.

Movie: A primary T cell becomes activated on a glass supported lipid bilayer containing its natural ligands. T cell receptor (TCR) molecules, labeled with enhanced green fluorescent protein (eGFP), form microclusters at the entire the contact site between T cell and bilayer. TCR microclusters are transported towards the center of the contact site in an actin dependent fashion and form the center of an immunological synapse. The movie was acquired in total internal reflection (TIRF) mode to eliminate intracellular fluorescence.

"While signal transduction is traditionally seen as a
sequence of protein interactions and modifications, it
has become clear that these events are also spatially
controlled through plasma membrane compartmentalization.
To further understand this, my lab studies the
architecture of the plasma membrane in general, as
well as its contribution to signal transduction in T cells."

In eukaryotes, the plasma membrane–a double layer of lipid
molecules that encloses all cells–not only segregates the cell from its
environment, but also serves as the principal
interface for communication between cells.
Not surprisingly, the plasma membrane's
structure and properties impact many biological
processes. T cells, whose main job is
to fight infection, for example, utilize and
reorganize their plasma membrane constantly
during activation and effector functions.
This is most dramatically seen in the establishment
of signaling microclusters and
the formation of the immunological synapse
between T cells and antigen-presenting cells
upon activation of the former by the latter.

Despite a lot of interest in the past in the precise
architecture of the plasma membrane,
studies of plasma membrane-associated
signaling had been hampered by technical
barriers such as cell lysis and limited resolution
in microscopy. Lillemeier overcame
these limitations through the use of novel
high-resolution imaging techniques such as
photo-activated localization microscopy
(PALM) and dual color fluorescence crosscorrelation
spectroscopy (dcFCCS), which
allowed him to observe directly the spatial
and temporal distribution of membrane-associated
molecules on a nanometer scale.

He discovered that all membrane-associated
proteins in the cells that he examined are
clustered into what he refers to as "protein
islands," which led him to postulate a
novel concept for the general architecture
of plasma membranes. Lillemeier also found
that the T cell receptor signaling cascade is
spatially and temporally controlled through
the segregation and association of distinct
membrane microdomains (protein islands)
that contain specific subsets of T cell signaling
molecules. He believes that this type of
signal control may be a general feature of
membrane-associated signaling and is probably
used in a variety of signaling processes.

Lillemeier will expand his research to understand
how this higher order in the plasma
membrane is achieved and what molecular
mechanisms are in place to utilize it during
signal transduction. His studies will help
to expand knowledge of spatio-temporal
signaling control, which will suggest new approaches
in manipulating the response of the
immune system to pathogens and diseases.

Awards and Honors

National Institutes of Health (NIH) Director's New Innovator Award (2012)